Every art show consists of at least two elements: a defining concept and the art. The concept can be so straightforward as not to seem conceptual. For a career retrospective, the concept is, duh, the artist’s career. Sometimes, though, the concept can get tricky. That’s the case with “Reality Check,” which runs at the Massachusetts College of Art and Design through Dec. 7.

Usually, the trickier the concept, the farther-fetched the show — and the more dubious the art. That’s not the case here. The concept, photographs that look digitally altered but aren’t, is both intriguing and provocative. It turns upside down any number of assumptions that have become prevalent in looking at images. And the art is often spectacular.

Consider the four big color images from Stephen Mallon’s “Next Stop Atlantic” series. Mallon documents the process of placing New York subway cars in the ocean to form reefs. Subway cars? Ocean? This must be Photoshop. Except that it’s not. What’s seen is as real as you or I — and, with all due respect, a whole lot more interesting to look at. In “Wave,” the stack of cars could be some metallic, right-angled sea creature giving off a massive spume. Or, for the more asethetically inclined, it might recall some weird variant on Frederic Edwin Church’s iceberg paintings.

Water plays an even more important role in Matthew Brandt’s “Lakes and Reservoirs” series. It both provides subject and alters outcome. Once he’s made a print, Brandt soaks it in water taken from the lake or reservoir in the photograph. The distressed images that result look much more like paintings than photographs, but photographs they are — and often startlingly attractive.

Attractiveness is not what Angela Strassheim or Chris McCaw is after. Strassheim, who worked for many years as a police forensic photographer, takes very long exposures of the interiors of houses where murders have been committed. She uses only ambient light. The results represent a noir beyond noir: grim, forbidding, foreboding.

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Conversely, it’s not darkness but light that draws McCaw. Literal light: He makes long exposures of the course of the sun over time, anywhere from 15 minutes to 24 hours. He uses very powerful lenses, so that in places the light burns through the photographic paper. The images (if that is the right word) appear almost sculptural at times, with the way that their surfaces have been affected. Talk about distressed! They could be portals to some spooky elsewhere.

Light is Christina Seely’s subject, too, only it’s human rather than solar in origin. Her series “Lux” records light pollution in some four dozen of the world’s largest cities. These megalopolises glow with a literally unearthly light. Seely’s images may look like pure artifice, but they are in fact pure documentation. They have the bewitching brightness of lightboxes — except that these lightboxes capture light rather than produce it — and are elegantly gorgeous.

Riotous color populates the pictures of both Daniel Gordon and Gastón Ugalde. Gordon finds images online that he likes, prints them out, and reworks them, origami-like, into large objects. He arranges these objects into tableaux and photographs them. The results are highly garish, with a funhouse, Candy Land quality. He could consider moonlighting as a board game designer.

Ugalde’s use of color is far more selective, strikingly so. For his “Happy” series, he photographs the immense Salar de Uyuni salt flats, in his native Bolivia. The setting is astonishing, yet Ugalde manages to up the ante on its astonishingness. He takes a set of highly colorful props — balloons, cloths, papers — and captures the results once he’s thrown them in the air. The visual incongruity rivals that of Mallon’s aquatic subway cars, only here the effect is celebratory. The cars are sinking, or about to. The colors look as though they could hover forever. Not that they can, of course. As the ultimate reality check, gravity defers only to death.